Optimization of Shallow Gas Cementing Design for RAG Wells in Austria

Research output: ResearchMaster's Thesis

Abstract

This thesis represents the first step by improving cementing operations with shallow gas layers in Austria by optimizing cement design for the company Rohöl-Aufsuchungs Aktiengesellschaft (RAG). The main objective of this master thesis was to analyze, evaluate and find possibilities to improve shallow gas cementing operations with special focus on different types of cement. Therefore the thesis was split in different parts. Firstly general important aspects of cementing operations were covered as gas migration theory, hydration phases of cements, mud removal, casing centralization or cement properties. Followed by a case study analyzing cementing operations of 15 wells in known critical areas where the focus was set to different cement systems, temperature influence by summer or winter time and different use of Mudpush II and Scavenger. Third part was used to cover cementing operation simulations which are done before any cementing job to evaluate the gas migration risk using mudlog results, volumes, pump pressures and as well the used cement additives. In the last part the three different cement systems used for cementing the surface or intermediate casing sections were analyzed. First all possible laboratory test as rheology measurements, fluid loss, free fluid, ultrasonic cement analyzer and consistometer testing were performed in Vechta. Secondly the different cement systems were tested in Leoben to determine the difference between them with focus on the cement shrinkage and hydrostatic pressure transmission of fluid columns above the cement to determine how long hydrostatic pressure of the cement and fluid above is applied against the formation containing gas layers. The results showed two different reasons why the usage of Class G cement in combination with GasBLOK additives or EasyBLOK cement systems is warrantable compared to Cem I 42.5 cement. These two systems show a higher tendency to act like right angle set cement systems and the shrinkage of the cement during the hydration is lower which as well reduces the risk of gas migration into the annulus by not creating any migration paths and reducing the pressure.

Details

Original languageEnglish
Supervisors/Advisors
Award date28 Jun 2013
StatePublished - 2013